Conventional actuating mechanisms for circuit breakers typically include a collapsible toggle assembly which links an actuator, such as a manually movable switch, with a displaceable contact arm carrying one of the circuit breaker contacts so that manual movement of the switch causes the contacts to open or close. In a conventional arrangement, the toggle assembly includes two pivotally connected links and a releasable latch which is carried on the pivotable links for releasably latching the two pivotable links of the toggle assembly in a rigid uncollapsed position. One of the toggle assembly links is coupled to the manual actuator and the other link is coupled to the displaceable contact arm so that the movement of the manual actuator from one position to another causes the displacement of the rigidly held collapsible toggle assembly which, in turn, displaces the contact arm to open or close the contacts.
The conventional circuit breaker also includes an electro-magnetically actuated mechanical trip actuator to open the contacts of the circuit breaker under overload conditions. For this purpose, an electro-magnetic portion senses overload conditions and a mechanical portion engages and trips the normally rigid toggle assembly to collapse it and open the circuit breaker contacts. To trip the releasable latch which normally holds the toggle assembly rigid, the mechanical trip portion of the actuator includes a displaceable trip element. When an overload condition is sensed, the trip element is displaced by electro-magnetic forces into engagement with the latch causing the latch to release. When the latch is released, the toggle assembly collapses permitting the contacts of the circuit breaker mechanism to open.
One of the problems with conventional actuating mechanisms is that the latch is not held in a fixed position on the frame. Since the latch is typically carried on the pivotal links of the toggle assembly, the latch moves during the collapse of the toggle assembly. As a result, there can be a variation in the position where the trip element engages and releases the movable latch causing a margin of error to be introduced into the system. To compensate for possible variations in the engagement position, increased tolerances must be engineered into the design of the actuating mechanism to ensure that the circuit breakers, which are often mass produced, properly function within the proper specifications.
In accordance with the present invention, a unique actuating mechanism for a circuit breaker is provided which overcomes the inherent design problems associated with conventional actuating mechanisms.